Power-efficient Tuning of Electro-optically Tunable Reflection-type Transversal Filter Laser with Control Electronics

Tuning power consumption of a tunable laser (TL) increasingly becomes an issue as the application range of wavelength division multiplexing grows in optical communications. On-chip Joule heat of a micro-heater commonly employed for a recent coherent TL needs to be exhausted out of the laser chip. It results in an increase in power consumption of laser control electronics with a thermal electric cooler (TEC) driver. An electro-optically TL whose laser wavelength is tuned by the electro-optic (EO) effect is advantageous for power-efficient tuning caused by little Joule heat during tuning unlike a micro-heater-based TL. We developed an electro-optically TL using a reflection-type transversal filter (RTF) whose reflection spectrum is tuned by the quantum-confined Stark effect (QCSE) known as a kind of the EO effect. In this paper, we describe an RTF laser with power-efficient control electronics thanks to little Joule heat from an RTF laser, which suppresses TEC driver power consumption. While an issue of control electronics of an RTF laser is a larger negative voltage (-15 V) for the QCSE than the industrial standard +3.3 V voltage supply, we found low-noise laser operation of an RTF laser to which reverse voltages are supplied from control electronics with an inverting switching converter based on the Ćuk topology. As a result, we successfully achieve wavelength-channel-dependent power consumption of less than 150 mW of an RTF laser with control electronics. Practical light source performance for a 400G digital coherent modulation format is also demonstrated.